1. Field
The present invention relates to an apparatus, system, and method of inspecting an image formed by an image forming apparatus, and a recording medium storing an image inspection control program.
2. Background
The recent image forming system may be provided with an inspection apparatus, which reads a printed image output from an image forming apparatus, generates a master image from image data of the printed image, and compares the read image with the master image to determine whether the printer image sufficiently reproduces the image data. To compare between the read image and the master image, each pixel in the read image needs to be compared with a corresponding pixel in the master image. In view of this, the pixel position of the master image may be corrected so as to match the pixel position of the read image, which may shrink in size or may be skewed during print processing, by enlarging or reducing the size of the master image or rotating the master image. For example, the inspection apparatus may specify a plurality of reference points in the read image, which correspond to a plurality of reference points in the master image, by pattern matching. Based on the positional shifts of the reference points between the read image and the master image, a correction parameter to be used for correcting the master image may be set. This technique of correcting the positional shift in the read image based on pattern matching is, however, time consuming and requires high computation loads.
Japanese Patent Application Publication No. 2005-223515 discloses an inspection apparatus, which previously calculates a correction parameter for correcting the positional shift of the read image attributable to the stationary noise. The calculated correction parameter is used to correct the read image before correcting the read image based on pattern matching as described above, thus reducing the processing time.
This technique described in Japanese Patent Application Publication No. 2005-223515 has drawbacks such that the calculated correction parameter is not able to correct the positional shift due to the non-stationary noise, such as the noise attributable to the temporal change in print processing. For example, it is assumed that the degree of shrinking or skewing of the printed image tends to change, depending on the operation conditions of the image forming apparatus such as an accumulated operation time of the image forming apparatus. If the positional shift of the read image becomes greater as the operation time of the image forming apparatus increases, the processing time and the computation loads that are required for inspecting the printed image increase as well.